Azure Access Control Service (ACS) is an extension of Windows Identity Foundation (WIF) onto Windows Azure. It provides for a single access point for authentication users against various authentication providers (Live, Google, Yahoo, Facebook)

Here are the steps to enable ACS

Login to Windows Azure portal (windows.azure.com)

Click on “Service Bus, Access Control Service & Caching” at the bottom left of the screen

Click on “Access Control” on the top left of the screen

Click on “New namespace” at the top left of the screen

Enter your namespace, this determines the final url (e.g abc)

For country/region, select the region closest to where your customers are

Click on “Create Namespace”

You will have to wait a while for the namespace to be created. Once it is done it will show the status as “Active”